CoTMP: Page 197

To further explain, a cross-up in a fighting game is when a character switches sides and attacks at the same time. In traditional fighting games, a character can only block by holding the control stick away from their opponent, so if they switch sides, then they must reverse their input to continue blocking. However, cross-ups can happen so fast that one might not be prepared to make such an adjustment so quickly. However, it seems that ZeRo is already predicting it.